My wife and I have a pair of Jialing NP50-GL's that I installed 110cc engines in them a few years ago. They will do 53 mph (GPS verified) with my 220+ lbs butt riding them. I have a 17 tooth sprocket up front and the stock sprocket at the rear. They are great little bikes. They were a terrific learning bike for my wife when she first got her motorcycle license. Here is a picture when they still had the 50cc engines. I had to remove the front fenders when I installed the new engines, as they would not clear the extended head of the engine.